ATP and cancer immunosurveillance
2021; Springer Nature; Volume: 40; Issue: 13 Linguagem: Inglês
10.15252/embj.2021108130
ISSN1460-2075
AutoresOliver Kepp, Lucillia Bezu, Takahiro Yamazaki, Francesco Di Virgilio, Mark J. Smyth, Guido Kroemer, Lorenzo Galluzzi,
Tópico(s)Autophagy in Disease and Therapy
ResumoReview14 June 2021free access ATP and cancer immunosurveillance Oliver Kepp Oliver Kepp orcid.org/0000-0002-6081-9558 Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Search for more papers by this author Lucillia Bezu Lucillia Bezu Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Search for more papers by this author Takahiro Yamazaki Takahiro Yamazaki Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA Search for more papers by this author Francesco Di Virgilio Francesco Di Virgilio orcid.org/0000-0003-3566-1362 Department of Medical Sciences, University of Ferrara, Ferrara, Italy Search for more papers by this author Mark J Smyth Mark J Smyth Immunology in Cancer and Infection Laboratory, QIMR Berghofer Medical Research Institute, Herston, Brisbane, Qld, Australia Search for more papers by this author Guido Kroemer Corresponding Author Guido Kroemer [email protected] orcid.org/0000-0002-9334-4405 Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France Suzhou Institute for Systems Medicine, Chinese Academy of Medical Sciences, Suzhou, China Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, SwedenThese authors contributed equally to this work as senior authors Search for more papers by this author Lorenzo Galluzzi Corresponding Author Lorenzo Galluzzi [email protected] orcid.org/0000-0003-2257-8500 Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA Sandra and Edward Meyer Cancer Center, New York, NY, USA Caryl and Israel Englander Institute for Precision Medicine, New York, NY, USA Department of Dermatology, Yale School of Medicine, New Haven, CT, USA Université de Paris, Paris, FranceThese authors contributed equally to this work as senior authors Search for more papers by this author Oliver Kepp Oliver Kepp orcid.org/0000-0002-6081-9558 Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Search for more papers by this author Lucillia Bezu Lucillia Bezu Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Search for more papers by this author Takahiro Yamazaki Takahiro Yamazaki Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA Search for more papers by this author Francesco Di Virgilio Francesco Di Virgilio orcid.org/0000-0003-3566-1362 Department of Medical Sciences, University of Ferrara, Ferrara, Italy Search for more papers by this author Mark J Smyth Mark J Smyth Immunology in Cancer and Infection Laboratory, QIMR Berghofer Medical Research Institute, Herston, Brisbane, Qld, Australia Search for more papers by this author Guido Kroemer Corresponding Author Guido Kroemer [email protected] orcid.org/0000-0002-9334-4405 Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France Suzhou Institute for Systems Medicine, Chinese Academy of Medical Sciences, Suzhou, China Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, SwedenThese authors contributed equally to this work as senior authors Search for more papers by this author Lorenzo Galluzzi Corresponding Author Lorenzo Galluzzi [email protected] orcid.org/0000-0003-2257-8500 Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA Sandra and Edward Meyer Cancer Center, New York, NY, USA Caryl and Israel Englander Institute for Precision Medicine, New York, NY, USA Department of Dermatology, Yale School of Medicine, New Haven, CT, USA Université de Paris, Paris, FranceThese authors contributed equally to this work as senior authors Search for more papers by this author Author Information Oliver Kepp1,2, Lucillia Bezu1,2, Takahiro Yamazaki3, Francesco Di Virgilio4, Mark J Smyth5, Guido Kroemer *,1,2,6,7,8 and Lorenzo Galluzzi *,3,9,10,11,12 1Equipe labellisée par la Ligue contre le cancer, Centre de Recherche des Cordeliers, INSERM U1138, Sorbonne Université, Université de Paris, Paris, France 2Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France 3Department of Radiation Oncology, Weill Cornell Medical College, New York, NY, USA 4Department of Medical Sciences, University of Ferrara, Ferrara, Italy 5Immunology in Cancer and Infection Laboratory, QIMR Berghofer Medical Research Institute, Herston, Brisbane, Qld, Australia 6Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France 7Suzhou Institute for Systems Medicine, Chinese Academy of Medical Sciences, Suzhou, China 8Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, Sweden 9Sandra and Edward Meyer Cancer Center, New York, NY, USA 10Caryl and Israel Englander Institute for Precision Medicine, New York, NY, USA 11Department of Dermatology, Yale School of Medicine, New Haven, CT, USA 12Université de Paris, Paris, France *Corresponding author. Tel: +33 1 4427 7667; E-mail: [email protected] *Corresponding author. Tel: +1 646 962 2095; E-mail: [email protected] The EMBO Journal (2021)40:e108130https://doi.org/10.15252/embj.2021108130 This article is part of the Cancer Reviews 2021 series. PDFDownload PDF of article text and main figures. ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions Figures & Info Abstract While intracellular adenosine triphosphate (ATP) occupies a key position in the bioenergetic metabolism of all the cellular compartments that form the tumor microenvironment (TME), extracellular ATP operates as a potent signal transducer. The net effects of purinergic signaling on the biology of the TME depend not only on the specific receptors and cell types involved, but also on the activation status of cis- and trans-regulatory circuitries. As an additional layer of complexity, extracellular ATP is rapidly catabolized by ectonucleotidases, culminating in the accumulation of metabolites that mediate distinct biological effects. Here, we discuss the molecular and cellular mechanisms through which ATP and its degradation products influence cancer immunosurveillance, with a focus on therapeutically targetable circuitries. Introduction According to a widely accepted model, malignant transformation is initiated by relatively common genetic or epigenetic alterations that incapacitate tumor-suppressing mechanisms (for the most part, mechanisms that ensure the preservation of cellular homeostasis) as they activate oncogenic drivers (generally, processes that enable accrued anabolism in support of hyperproliferation) (Hanahan & Weinberg, 2011; Timp & Feinberg, 2013). The vast majority of newly formed malignant cells, however, appears to be controlled by the host immune system prior to forming symptomatic tumors (Vesely & Schreiber, 2013; Lopez-Otin & Kroemer, 2021). While in most cases such control involves the definitive “eradication” of malignant cell precursors, in some instances newly formed cancer cells can resist immune attacks and generate a rudimentary tumor microenvironment that enables some degree of proliferation, a dynamic battle between emerging tumors and their host commonly referred to as “equilibrium” (Vesely & Schreiber, 2013). In this context, malignant cells can acquire additional genetic and epigenetic alterations that either (i) impair their ability to initiate anticancer immune responses, such as the loss or downregulation of genes coding for endogenous danger signals, (ii) limit their visibility to immune effector cells, such as the loss of MHC class I-coding genes or beta-2-microglobulin (B2M), (iii) increase their resistance to immune effector molecules, such as the loss of caspase 8 (CASP8), or (iv) establish a state of local immunosuppression, such as the upregulation of CD274 (best known as PD-L1) (Galluzzi et al, 2018). In this context, the equilibrium between cancer cells and the host immune system ceases to exist in favor of an “escape” phase culminating in uncontrolled tumor growth and metastatic dissemination (Dunn et al, 2002; Dersh et al, 2021). Importantly, the TME of malignancies that escaped immunosurveillance (Rao et al, 2019) undergoes a considerable reconfiguration, generally involving the accumulation of immunosuppressive myeloid and lymphoid cells including M2-like tumor-associated macrophages (TAMs) and CD4+CD25+FOXP3+ regulatory T (TREG) cells at the expense of M1-like TAMs, type I conventional dendritic cells (cDC1s), TH1 CD4+ T cells, CD8+ cytotoxic T lymphocytes (CTLs), and natural killer (NK) cells, all of which promote tumor-targeting immunity (Talmadge & Gabrilovich, 2013; Mantovani et al, 2017; Lee & Radford, 2019; Sprooten et al, 2019; Togashi et al, 2019). Beyond such a general trend, however, the precise immune contexture of each neoplasm exhibits considerable heterogeneity (De Sousa et al, 2013; Vitale et al, 2021) and has a major impact on disease course and response to therapy (Fridman et al, 2017). Indeed, it has now become clear that the efficacy of most anticancer agents commonly employed in the clinic, encompassing cytotoxic chemotherapeutics, radiation therapy (RT), and targeted anticancer agents, relies at least partially on the (re)activation of immunosurveillance (Galluzzi et al, 2020; Rodriguez-Ruiz et al, 2020; Petroni et al, 2021). In line with this notion, considerable efforts are being dedicated to the identification of clinically relevant approaches to alter the TME in favor of treatment efficacy, especially for tumors that exhibit rather scarce infiltration by immune effector cells, such as luminal breast cancer and pancreatic carcinoma (Kroemer et al, 2015; Ho et al, 2020). All cellular components of the TME including malignant and immune cells engage in a dynamic competition for nutrients, oxygen, and trophic signals (all of which are generally scarce as a consequence of relatively poor vascularization) (Martinez-Outschoorn et al, 2017; O'Sullivan et al, 2019; Garner & de Visser, 2020). Moreover, the availability of nutrients, oxygen, and trophic signals is not equal across all tumor regions and is not constant over time (e.g., before and after therapy), hence constituting a major driver of intratumoral heterogeneity (ITH) (De Sousa et al, 2013; Vitale et al, 2021). Indeed, such restrictions de facto operate as Darwinian pressures, fostering the selection of cells with an accrued capacity to harness alternative carbon sources (e.g., lactate, extracellular amino acids) for catabolic and anabolic reactions in support of proliferation and tolerance to hypoxia (Chang et al, 2015; Xiao et al, 2019). Adenosine triphosphate (ATP) occupies a key position in the overall configuration of the TME. On one hand, intracellular ATP is crucial for each cellular TME component to survive and mediate its functions (including proliferation, for malignant and non-terminally differentiated immune cells) (Leone & Powell, 2020; Bergers & Fendt, 2021). On the other hand, the pool of ATP that accesses the TME upon active secretion by living or dying cells into the extracellular space constitutes a major signal transducer (Di Virgilio et al, 2018). The net effect of ATP signaling on the TME, however, depends on multiple factors, including the presence of extracellular ATP-degrading enzymes as well as the expression pattern of purinergic receptors. Here, we will critically discuss the molecular and cellular mechanisms through which extracellular ATP and its degradation products influence the crosstalk between malignant and immune cells and present recent advances on the purinergic system as a potential target for the development of novel anticancer interventions. Extracellular ATP homeostasis in the TME Since ATP cannot be synthesized in the extracellular milieu, the microenvironmental levels of ATP are entirely controlled by the balance between its secretion/release and degradation (Fig 1). Figure 1. Extracellular ATP homeostasis in the tumor microenvironment The concentration of extracellular ATP in the tumor microenvironment is determined by the balance between ATP release and degradation. A variety of cells release ATP either as part of their physiological state or as they respond to stress and potentially die, including cancer cells, dendritic cells (DCs), tumor-infiltrating neutrophils (TINs), tumor-associated macrophages (TAMs), and platelets. Extracellular ATP is catabolized by the sequential activity of ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1, best known as CD39), which converts ATP into ADP and AMP, and 5'-nucleotidase ecto (NT5E, best known as CD73), which converts AMP into adenosine (ADO). CD39 and CD73 are expressed by multiple cell type that populate the tumor microenvironment, including some malignant cells, cancer-associated fibroblasts (CAFs), exhausted cytotoxic T lymphocytes (CTLs), regulatory T (TREG) cells, an immunosuppressive subset of natural killer (NK) cells, M2-like TAMs, and myeloid-derived suppressor cells (MDSCs). Hypoxia is a major driver of ATP degradation in the tumor microenvironment. Download figure Download PowerPoint Adenosine triphosphate secretion is an active, regulated process that can occur via multiple mechanisms and involve different cellular sources. Molecular mechanisms for ATP secretion encompass: (i) exocytosis of ATP-containing vesicles, a process that may (but does not necessarily) involve cell death (Imura et al, 2013; Martins et al, 2014) and mechanistically relies on vesicular loading by solute carrier family 17 member 9 (SLC17A9) (Imura et al, 2013; Cao et al, 2014) and the SNAP receptor (SNARE)- and Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)-dependent fusion of exocytosis-competent ATP-rich vesicles with the plasma membrane (Imura et al, 2013; Martins et al, 2014); (ii) liberation of cytosolic ATP molecules via gap junction protein alpha 1 (GJA1, best known as CX43) hemichannels at gap junctions (Stout et al, 2002; Eltzschig et al, 2006; Kang et al, 2008); and (iii) gradient-driven efflux via oligomeric pannexin 1 (PANX1) channels (also known as “pannexons”) (Dahl, 2015), which are sensitive to activation by mechanical forces (Bao et al, 2004), by the pro-inflammatory CASP1 (Narahari et al, 2021), and by apoptotic caspases such as CASP3 and CASP7 (Chekeni et al, 2010; Medina et al, 2020). That said, while both vesicular ATP secretion and PANX1-dependent release have been documented in living and dying malignant cells (Martins et al, 2014; Martin et al, 2017), CX43 hemichannels appear to be mostly operational in non-malignant cells of the TME, including astrocytes (Stout et al, 2002), as well as (at least potentially) neutrophils (Dosch et al, 2018) and macrophages (Dosch et al, 2019). Indeed, while both neutrophils and macrophages have been shown to release ATP via CX43 hemichannels in non-oncological settings, whether such function is preserved in TAMs and tumor-infiltrating neutrophils (TINs) remains to be elucidated. Along similar lines, platelets are known as major sources of extracellular ATP upon degranulation (Yeaman, 2014), but their contribution to extracellular ATP availability in the TME has just begun to emerge (Schumacher et al, 2013; Gaertner & Massberg, 2019). Additional cellular compartments that may secrete ATP in the TME encompass (at least in some settings) endothelial cells (Sáez et al, 2018; Yang et al, 2020d), fibroblasts (Pinheiro et al, 2013; Murata et al, 2014), dendritic cells (DCs) (Tappe et al, 2018; Martinek et al, 2019), and activated CTLs (Tokunaga et al, 2010). Importantly, while some cells spontaneously secrete at least some ATP in their physiological status, for the most part, ATP is actively released in the context of adaptive responses to microenvironmental perturbations, including mechanical cues (Bao et al, 2004), inflammatory signals (Beckel et al, 2018), hypoxia (Lim To et al, 2015), and exposure to a variety of cancer therapeutics (Michaud et al, 2011; Tatsuno et al, 2019; Rodriguez-Ruiz et al, 2020). In most such instances, abundant ATP secretion by stressed cells (which is key for extracellular ATP to mediate immunostimulatory effects, see below) involves functional autophagic responses (Michaud et al, 2011), potentially linked to the ability of autophagy to preserve intracellular ATP pools during stress (Rybstein et al, 2018; Anderson & Macleod, 2019). Consistent with this notion, genetic and pharmacological interventions aimed at blocking or boosting autophagic responses in cancer cells have been consistently associated with reduced and increased ATP secretion, respectively, in response to immunogenic chemotherapy (Michaud et al, 2011; Pietrocola et al, 2016; Chen et al, 2019; Kepp & Kroemer, 2020; Wang et al, 2020). Obviously, all dying cells abruptly release their cytosolic ATP pool when they undergo plasma membrane permeabilization (PMP) as the final step of cellular demise. However, while PMP itself has now been shown to be an active (rather than an osmosis-driven) process even in the context of post-apoptotic, secondary necrosis (Kayagaki et al, 2021), the consequent spillage of cytosolic content into the extracellular milieu remains a largely unregulated phenomenon. Extracellular ATP is rapidly catalyzed by the sequential activity of two ectonucleotidases, that is, ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1, best known as CD39), which converts ATP into ADP and AMP, and 5'-nucleotidase ecto (NT5E, best known as CD73), which converts AMP into adenosine as the rate-limiting step of this enzymatic cascade (Allard et al, 2020; Moesta et al, 2020). CD39 is mostly expressed by TREG cells (Borsellino et al, 2007), M2-like TAMs (d'Almeida et al, 2016), and myeloid-derived suppressor cells (MDSCs, an immature population of myeloid cells with potent immunosuppressive activity) (Li et al, 2017), as well as by specific cancer cell types, such as adult T-cell leukemia/lymphoma cells (Nagate et al, 2021), type 16 human papillomavirus (HPV-16)-associated cervical carcinoma cells (de Lourdes Mora-García et al, 2019), and ovarian carcinoma cells (Häusler et al, 2011). Moreover, CD8+ CTLs undergoing terminal exhaustion as a consequence of chronic antigen stimulation generally exhibit a CD39+ phenotype (Canale et al, 2018). Conversely, CD73 is expressed by a wide variety of malignant cells as well as by cancer-associated fibroblasts (CAFs) (Yu et al, 2020), TREG cells (Stagg et al, 2011), and a regulatory subset of NK cells (Neo et al, 2020). Interestingly, the whole-body deletion of purinergic receptor P2X 7 (P2RX7), which codes for one of the main receptors of extracellular ATP, has a major impact on extracellular ATP levels in the TME of experimental P2RX7-competent melanomas (De Marchi et al, 2019), at least in part as a consequence of altered tumor infiltration by CD39+ and CD73+ TREG cells and decreased ATP release by TAMs (De Marchi et al, 2019). Such an effect, however, cannot be recapitulated by the pharmacological P2RX7 antagonist A740003 as a result of its mixed activity on immune cells (it fails to alter tumor infiltration by TREG cells, decreases the abundance of intratumoral CD39+ and CD73+ effector T (TEFF) cells, and inhibits ATP secretion by TAMs) and malignant cells (it favors ATP secretion by malignant cells) (De Marchi et al, 2019). Of note, extracellular ATP degradation does not necessarily require the expression of CD39 and CD73 on the same cell (in cis), but can also occur efficiently when these ectonucleotidases are expressed by different cellular compartments that are in proximity to each other within the TME (Schuler et al, 2014). CD73 is abundant in TREG cell-derived exosomes (Smyth et al, 2013), which are highly mobile and hence further promote the overall catalytic efficiency of ATP degradation within the TME. Moreover, CD38 (also known as cyclic ADP-ribose hydrolase) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which are expressed by some cancer cells and exhausted T cells, can compensate for limited CD39 activity as they catalyze the conversion of extracellular NAD+ into ADP ribose and AMP (Morandi et al, 2015). Finally, the expression of both CD39 and CD73 can be upregulated by hypoxia, which is relatively common in the TME of solid neoplasms, via a transcriptional mechanism that involves hypoxia-inducible factor 1 subunit alpha (HIF1A, best known as HIF-1α) (Giatromanolaki et al, 2020; Synnestvedt et al, 2002). In summary, the levels of extracellular ATP in the TME are dynamically determined by the mutually opposed inputs of secretion/release vs. degradation. As the factors governing these aspects of the ATP biology exhibit a considerable degree of ITH, regional and temporal fluctuations in extracellular ATP levels are likely to play a major role in the outcome of purinergic signaling in the TME, as discussed further below. Immunostimulation by extracellular ATP Extracellular ATP mediates two main functions: (i) It operates as a chemotactic cue for myeloid cells, upon binding to the purinergic receptor P2Y2 (P2RY2), a metabotropic receptor (Elliott et al, 2009; Chekeni et al, 2010), and (ii) it promotes activation of the inflammasome and hence CASP1-dependent secretion of interleukin 1 beta (IL1B) and IL18 upon binding to P2RX7, an ionotropic receptor (Perregaux et al, 2000). Importantly, both these effects are required for the optimal activation of tumor-specific immune responses by (and hence the complete efficacy of) immunogenic chemotherapeutics such as anthracyclines and oxaliplatin, as demonstrated in P2ry2 −/−, P2rx7 −/−, Casp1 −/− - and Il18 −/− mice, as well as mice lacking a core component of the inflammasome (Nlrp3 −/− mice), the main IL1B receptor (Il1r1 −/− mice) or treated with a purinergic receptor antagonist (suramin) or an IL1B-blocking antibody (Ghiringhelli et al, 2009; Aymeric et al, 2010; Ma et al, 2013). In this setting, DC precursors newly recruited to the TME via ATP released by cancer cells succumbing to immunogenic cell death (ICD) not only mature upon ATP-driven inflammasome activation and migrate to tumor-draining lymph nodes or tertiary lymphoid structures to prime adaptive anticancer immunity, but also recruit a population of IL17-producing γδ T cells that is critical for tumor infiltration by primed CTLs (Ma et al, 2011). In accordance with this notion, optimal anticancer immune responses (and consequent superior therapeutic efficacy) driven by immunogenic chemotherapeutics are compromised in Il17a −/− and Il17ra −/− mice (Ma et al, 2011). Intriguingly, it has recently shown that the chemotactic activity of ATP on DCs also involves P2RX7 and PANX1 (Saez et al, 2017), suggesting the existence of a feed-forward loop whereby intracellular ATP stores may contribute to DC migratory capacity (Saez et al, 2017). Moreover, elevated levels of extracellular ATP appear to induce pyroptosis in P2RX7+ M2-like TAMs, hence supporting T cell-mediated antitumor immunity upon the depletion of immunosuppressive cells from the TME (Bidula et al, 2019). Importantly, the net immunomodulatory effect of extracellular ATP depends on the activation of additional signaling pathways. Indeed, the PANX1-dependent co-release of ATP and a wide panel of metabolites including ADP, AMP, GMP, creatine, spermidine, and glycerol-3-phosphate (G3P) by dying cells reportedly promote the removal of cell corpses while preventing the initiation of inflammatory reactions (Medina et al, 2020; Narahari et al, 2021). Moreover, extracellular ATP can have direct tumorigenic functions. Specifically, the cancer cell-driven release of ATP from platelets initiates a P2RY2-dependent signaling cascade that promotes tumor extravasation and metastatic dissemination upon the opening of endothelial barriers (Schumacher et al, 2013; Chen et al, 2019; Wang et al, 2020). The autophagy-dependent secretion of ATP by melanoma cells has been shown to promote invasiveness and resistance to the BRAF inhibitor vemurafenib, a process that requires P2RX7 expression in the malignant cell compartment (Martin et al, 2017). Similar findings have been obtained with human triple-negative breast cancer (TNBC) MDA-MB-231 cells upon the ATP-dependent activation of the transcription factor SRY-box transcription factor 9 (SOX9) (Yang et al, 2020a). Finally, NME/NM23 nucleoside diphosphate kinase 1 (NME1, best known as NDPK-A) and NME2 (best known as NDPK-B) expression on extracellular vesicles from MDA-MB-231 cells reportedly support the formation of pulmonary metastatic niches as a consequence of extracellular ATP generation in situ and consequent activation of purinergic receptor P2Y1 (P2RY1) (Duan et al, 2021). Consistent with the multipronged effects of extracellular ATP on the TME, a large body of clinical literature suggests that genetic or epigenetic defects affecting ATP signaling influence disease outcome in cancer patients in a context-dependent manner (Table 1). For instance, while loss-of-function polymorphisms in P2RX7 (rs3751143; rs208294) have been associated with advanced stage or poor disease outcome in cohorts of patients with breast carcinoma (Ghiringhelli et al, 2009), chronic lymphocytic leukemia (CLL) (Thunberg et al, 2002; Wiley et al, 2002; Zhang et al, 2003), and papillary thyroid carcinoma (PTC) (Dardano et al, 2009), no impact on clinicopathological variables could be attributed to rs3751143 in other cohorts of subjects with CLL (Starczynski et al, 2003; Nückel et al, 2004), multiple myeloma (Paneesha et al, 2006), and PTC (Dardano et al, 2009), while increased expression levels of P2RX7 have been linked to disease progression in an independent cohort of CLL patients (Adinolfi et al, 2002). Likewise, elevated P2RY2 levels have been associated with gastric malignant transformation (Aquea et al, 2014). A variety of immunohistochemical and transcriptional signatures of proficient autophagic responses have been linked to worsened disease outcome in cohorts of breast (Yamazaki et al, 2020), gastric (Kim et al, 2019; Wang et al, 2021), pancreatic (Ko et al, 2013; Cui et al, 2019), and head and neck (Jiang et al, 2012) cancer patients, while the contrary held true (or there was no impact on clinicopathological variables) in independent series of patients with breast (Ladoire et al, 2015; Tang et al, 2015; Ladoire et al, 2016), ovarian (Chen et al, 2020c), hepatocellular (Lee et al, 2013; Qin et al, 2018), gastric (Wang et al, 2021), colorectal (Li et al, 2020), and salivary gland (Li et al, 2019a) carcinoma. Table 1. Pathophysiological relevance of extracellular ATP signaling in human cancer. Cancer No. patients Variable Technology Impact References Breast cancer 225 P2RX7 rs3751143 SNP analysis Metastatic dissemination Decreased OS Ghiringhelli et al (2009) 1,067 1,992 BECN1 Gene expression profiling Improved disease outcome Tang et al (2015) 152 MAP1LC3B IHC Improved MFS Improved OS Ladoire et al (2016) 152 1,646 MAP1LC3B IHC Improved PFS Ladoire et al (2015) CLL 36 P2RX7 rs3751143 SNP analysis Disease stage Wiley et al (2002) 144 P2RX7 rs3751143 SNP analysis Marginally decreased OS Zhang et al (2003) 170 P2RX7 rs3751143 SNP analysis Decreased OS Thunberg et al (2002) 111 P2RX7 rs3751143 SNP analysis No correlation with clinical outcome Nückel et al (2004) 121 P2RX7 rs3751143 SNP analysis No correlation with clinical outcome Starczynski et al (2003) 21 P2RX7 Immunoblotting Disease progression Adinolfi et al (2002) Colorectal cancer 2,297 MAP1LC3B Gene expression profiling Increased OS Li et al (2020) Gastric cancer 14 P2RY2 Gene expression profiling Disease Aquea et al (2014) 354 MAP1LC3C Gene expression profiling Improved OS Wang et al (2021) 354 ATG4D Gene expression profiling Decreased OS Wang et al (2021) 402 MAP1LC3B and SQSTM1 IHC, immunoblotting a,nd RT–PCR Decreased OS Kim et al (2019) Head and neck cancer 79 MAP1LC3B IHC Disease stage Jiang et al (2012) Hepatocellular carcinoma 190 MAP1LC3B IHC Improved OS Lee et al (2013) 1,086 BECN1 Gene expression profiling Improved OS Qin et al (2018) Multiple myeloma 136 P2RX7 rs3751143 SNP analysis No correlation with clinical outcome Paneesha et al (2006) Ovarian cancer 1,497 BECN1 Gene expression profiling Improved OS and PFS Chen et al (2020c) 1,497 MAP1LC3B Gene expression profiling No correlation with clinical outcome Chen et al (2020c) Pancreatic cancer 73 BECN1 IHC Disease progression Ko et al (2013) 86 BECN1
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